Skip CI/RTD builds when the change is irrelevant (#4381)

- Add paths-ignore for docs/** and .readthedocs.yaml to the go, buf,
  kotlin, python, and typescript workflows so doc-only PRs don't
  spin up the Go test matrix.
- Add a Read the Docs post_checkout hook that exits 183 (the
  documented "cancel build successfully" code) for PR builds that
  don't touch docs/ or .readthedocs.yaml, mirroring the inverse on
  the RTD side.

Note: if any of the skipped checks are currently listed as required
in branch protection, doc-only PRs will block waiting for them. Flip
those to non-required, or add a matching no-op workflow that runs
under the ignored paths, as a follow-up.

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: kyleconroy

.github/workflows/buf.yml

@@ -1,5 +1,9 @@
 name: buf
-on: pull_request
+on:
+  pull_request:
+    paths-ignore:
+      - 'docs/**'
+      - '.readthedocs.yaml'
 jobs:
   build:
     runs-on: ubuntu-latest

.github/workflows/ci-kotlin.yml

@@ -3,7 +3,13 @@ on:
   push:
     branches:
       - main
+    paths-ignore:
+      - 'docs/**'
+      - '.readthedocs.yaml'
   pull_request:
+    paths-ignore:
+      - 'docs/**'
+      - '.readthedocs.yaml'
 jobs:
   build:
     if: false

.github/workflows/ci-python.yml

@@ -3,7 +3,13 @@ on:
   push:
     branches:
       - main
+    paths-ignore:
+      - 'docs/**'
+      - '.readthedocs.yaml'
   pull_request:
+    paths-ignore:
+      - 'docs/**'
+      - '.readthedocs.yaml'
 jobs:
   build:
     if: false

.github/workflows/ci-typescript.yml

@@ -3,7 +3,13 @@ on:
   push:
     branches:
       - main
+    paths-ignore:
+      - 'docs/**'
+      - '.readthedocs.yaml'
   pull_request:
+    paths-ignore:
+      - 'docs/**'
+      - '.readthedocs.yaml'
 jobs:
   build:
     if: false

.github/workflows/ci.yml

@@ -3,7 +3,13 @@ on:
   push:
     branches:
       - main
+    paths-ignore:
+      - 'docs/**'
+      - '.readthedocs.yaml'
   pull_request:
+    paths-ignore:
+      - 'docs/**'
+      - '.readthedocs.yaml'
 jobs:
   build:
     strategy:

.readthedocs.yaml

@@ -10,6 +10,14 @@ build:
   os: ubuntu-22.04
   tools:
     python: "3.11"
+  jobs:
+    post_checkout:
+      # Cancel PR builds that don't touch the docs.
+      # https://docs.readthedocs.io/en/stable/build-customization.html#cancel-build-based-on-a-condition
+      - |
+        if [ "$READTHEDOCS_VERSION_TYPE" = "external" ] && git diff --quiet origin/main -- docs/ .readthedocs.yaml; then
+          exit 183
+        fi
 
 # Build documentation in the docs/ directory with Sphinx
 sphinx: